access active directory for login destop form using C#

i want to make a login desktop form using C#2005 to make the user enter the username and password of the windows xp in this application and this application must check if this username and password valid or not , i give a code from msdn that make me do this but i have aproblem  the code is

using System;
using System.Text;
using System.Collections;
using System.DirectoryServices;


public class LdapAuthentication
{
    private string _path;
    private string _filterAttribute;

    public LdapAuthentication(string path)
    {
        _path = path;
    }

    public bool IsAuthenticated(string domain, string username, string pwd)
    {
        string domainAndUsername = domain + @"\" + username;
        DirectoryEntry entry = new DirectoryEntry(_path, domainAndUsername, pwd);

        try
        {
            //Bind to the native AdsObject to force authentication.
            object obj = entry.NativeObject;

            DirectorySearcher search = new DirectorySearcher(entry);

            search.Filter = "(SAMAccountName=" + username + ")";
            search.PropertiesToLoad.Add("cn");
            SearchResult result = search.FindOne();

            if (null == result)
            {
                return false;
            }

            //Update the new path to the user in the directory.
            _path = result.Path;
            _filterAttribute = (string)result.Properties["cn"][0];
        }
        catch (Exception ex)
        {
            throw new Exception("Error authenticating user. " + ex.Message);
        }

        return true;
    }

    public string GetGroups()
    {
        DirectorySearcher search = new DirectorySearcher(_path);
        search.Filter = "(cn=" + _filterAttribute + ")";
        search.PropertiesToLoad.Add("memberOf");
        StringBuilder groupNames = new StringBuilder();

        try
        {
            SearchResult result = search.FindOne();
            int propertyCount = result.Properties["memberOf"].Count;
            string dn;
            int equalsIndex, commaIndex;

            for (int propertyCounter = 0; propertyCounter < propertyCount; propertyCounter++)
            {
                dn = (string)result.Properties["memberOf"][propertyCounter];
                equalsIndex = dn.IndexOf("=", 1);
                commaIndex = dn.IndexOf(",", 1);
                if (-1 == equalsIndex)
                {
                    return null;
                }
                groupNames.Append(dn.Substring((equalsIndex + 1), (commaIndex - equalsIndex) - 1));
                groupNames.Append("|");
            }
        }
        catch (Exception ex)
        {
            throw new Exception("Error obtaining group names. " + ex.Message);
        }
        return groupNames.ToString();
    }
}



and when i am use it by

            LdapAuthentication ld = new LdapAuthentication("LDAP://rootDSE");
         ld.IsAuthenticated("isasrv", "aaa", "bbb");
which is the first argument is the server name , the seconde is the user name the third is the password
i take exception
The providers deose not support searching and canot search LDAP\\:rootDSE
,pleas help me .




and i am not sure about the active directory path is it true .

note this applcation in the msdn web site to a web application not to desktop application , i want to desktop abblication

thanx

moodyahmadAsked:
Who is Participating?
 
prakash_prkCommented:
could u check this plz.

LdapAuthentication ld = new LdapAuthentication("LDAP://isasrv");
ld.IsAuthenticated("isasrv", "aaa", "bbb");

also try the other overload fucntion of DirectoryEntry class as shown in the article.
http://www.codeproject.com/csharp/arbauthentication.asp

regards
prakash
0
 
moodyahmadAuthor Commented:
i am using visual studio 2005
0
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